Interactions among leguminous trees, crops and weeds in a no-till alley cropping system

Abstract

Trees improve the soil quality and their rapid growth in the tropics make agroforestry systems potentially effective for establishing low-input agricultural systems in this region. This study assessed the effects of the biophysical interactions among leguminous trees, weeds, cotton and maize in an alley cropping system. The experiment comprised six treatments and four replicates in randomised blocks. This design resulted in the following treatments, Clitoria + Gliricidia (C+G); Acacia + Gliricidia (A+G); Leucaena + Clitoria (L+C); Leucaena + Acacia (L+A), Leucaena + Gliricidia (L+G) and Control (no residues). In January 2010, cotton and maize were sown among the legumes in sub-plots of 10 x 4m. The comparison of the results for cotton and maize confirmed that the effects of the trees on productivity can be very different for different crops. The residues did not produce variations in the chemical indicators that would account for the differences among the treatments with respect to the performance of the cash crops or for the weeds. The sensitivity of some crops to the allelopathic effects induced by the tree residues is evident mainly in root growth, in nutrient uptake and in the growth of the shoot. The results presented here support the view that the criteria for the choice of tree species for agroforestry systems must go well beyond the potential to enhance soil fertility to obtain the best results from agroforestry systems.